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What are invasive species?

Invasive species are species that are not native to our region, which is usually defined as not here pre-European contact. Not all non-native species are invasive though.  For a species to be considered invasive, they would have a negative impact ecolgically, socially or economically.  They tend to grow rapidly, spread quickly and widely and can grow just about anywhere. Because these species did not evolve here, we don’t have the controls (insects, viruses, fungi, predators) that keep them in check in their own part of the world.


Why are invasive species a problem?

Invasive species are not native to our region and tend to favour disturbance, grow rapidly and are hard to get rid of , while outcompeting native species.  Because they arrive in Canada without their natural predators to keep them in balance, invasive plants and animals can spread rapidly.  Specific threats include:

  • decreased biodiversity
  • altered water flow and leading to erosion and/or less available water
  • creating and increasing the fire hazard
  • damage to roads and other built structures
  • reduction of crop yield
  • recreational & tourism trails/areas choked by invasive monocultures
  • decreased property values
  • a loss of medicinal plants and cultural practices (loss of wild edibles, loss of habitat for wildlife and fish)

How do invasive plants spread?

Improper disposal of garden waste
Although it might seem like a good idea to “recycle” your garden debris into a natural area, what you’re really doing is introducing plants that can smother, choke and otherwise ruin parks, greenways and other greenspace needed by wildlife – and enjoyed by people.

Unintentional dispersal (by direct growth)
Many invasive plants are rapid-growing and fast-spreading. English ivy, for example, can spread up to 4.5 metres in a single year.

Unintentional dispersal (by seed)
Many invasive plants are prolific seed producers. One purple loosestrife plant, for example, can produce 3 million seeds! These can then be dispersed by water, people, animals, vehicles, etc. to new areas.

Intentional introduction as garden ornamental
Many invasive plants got their start in someone’s garden. Most were exotics brought from other parts of the world. But here, they don’t have the same natural predators or checks to keep them under control and they literally go wild.

Why do people buy invasive plants?

Invasive plants can be pretty, but the problems they cause are not
Yellow flag is admired for its big blooms; periwinkle is a pretty ground cover and holly is a Christmas favourite. But each wreaks havoc in our parks and other natural areas by displacing native plant species needed by wildlife and/or by altering water flow, stealing nutrients and sunlight.

Invasive plants can be easy to grow and can grow quickly – but that’s also what makes them invasive
Sometimes, homeowners looking for a quick solution to a bare spot will choose a plant lauded as a “fast spreader” or a “vigorous self-seeder”. Unfortunately, invasive plants tend to spread or seed themselves right out of your garden and into the parks and natural spaces nearby.

Invasive plants can be readily available – but so are more appropriate alternatives
Many garden centres, supermarkets and corner stores continue to sell invasive species such as English ivy, English holly and lamium. But just because something is being sold doesn’t mean it’s a wise choice. Discriminating consumers who choose non-invasive alternatives can help change what’s for sale.

What can I do?

Learn to identify local invasive species in your area.

  • Remove and control invasive species on your property.
  • Attend local activities like hand-pulling days.
  • Do not purchase noxious weed seeds from suppliers or catalogues.
  • Contain creeping plants by growing them in containers.
  • Don't let invasive plants go to seed, or remove them from your property.
  • Grow alternative plant species by substituting less aggressive plants for non-native invaders.
  • Keep aggressive plants from escaping your garden or landscaped area.
  • Do not use roadside or "wild" plants in flower arrangements if you cannot identify them.
  • Clean equipment, tools, vehicles and footwear before leaving an area that is infested with invasive plants.
  • Organize a "weed-free" space, like a local schoolyard or roadway.
  • Report invasive plants to the Council at 604-935-7665

Invasive species are everyone’s problem, and need to be everyone’s solution. People are the  largest spreader of invasive species. You can make a difference!

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